Light emitting diodes (LEDs) are semiconductor devices which send and receive a signal by converting electricity into infrared light or visible light using characteristics of compound semiconductors or which are used as light sources.
Group III-V nitride semiconductors have received substantial attention as essential materials for light emitting devices such as light emitting diodes (LEDs) or laser diodes (LDs) due to physical and chemical properties thereof.
Such a light emitting diode does not contain environmentally harmful substances such as mercury (Hg) used in conventional lighting apparatuses such as incandescent lamps or fluorescent lamps and thus advantageously has superior eco-friendliness, long lifespan and low power consumption, thus serving as an alternative to conventional light sources.
FIG. 1 is a sectional view illustrating a conventional light emitting device.
Referring to FIG. 1, the light emitting device includes a substrate 10, an AlN layer 12, an n-type AlGaN layer 22, a multi quantum well (MQW) layer 24, a p-type AlGaN layer 26 and a p-type GaN layer 28. The MQW layer 24 emits light having an energy determined by an inherent energy band of a material constituting an active layer 24, based on recombination between holes injected through the p-type AlGaN layer 26 and electrons injected through the n-type AlGaN layer 22. The p-type GaN layer 28 is a portion of a p-type electrode, which is made of GaN.
In such a conventional light emitting device, among light emitted from the MQW layer 24, light directed toward the p-type GaN layer 28 is absorbed in the p-type GaN layer 28 and thus does not contribute to light emission of the light emitting device. Accordingly, there is a demand for a solution to this problem.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.